1. Field of the Invention
The invention relates to a process for making saturated dimeric ketones. More particularly, it relates to making such ketones by using a zeolite catalyst.
2. Discussion of the Prior Art
Currently, commercial processes require three synthesis steps, each with relatively low yield, to convert monomeric ketone, e.g. acetone, to saturated dimeric ketone, e.g. methylisobutyl ketone (MIBK), according to the following schemes: ##STR1##
Mesityl oxide is separated from Step (2) and hydrogenated over Ni or Cu-Cr catalyst to form MIBK.
In this synthesis, the following side reactions take place: ##STR2##
The formation of diisobutyl ketone byproduct is a result of further condensation of MIBK with acetone. Heavier ketones, such as C.sub.12 ketone, have also been observed in a Pd/resin bifunctional system (see German Pat. No. 1,260,454).
Direct synthesis of methylisobutyl ketone from acetone over bifunction catalysts, such as Pd/zeolite (Japanese Pat. Nos. 46-2009 and 46-2643), Pd/cation exchange resin (German Pat. No. 1,260,454), KOH-alumina-Pd (U.S. Pat. No. 2,499,172), and MgO-silica-Pd (British Pat. No. 1,015,003), has also been reported. The zeolite reported in the Japanese patents is faujasite, which will be shown hereinafter to yield much less of the dimeric ketone, e.g. the MIBK.
U.S. Pat. No. 3,998,898 discloses that acetone can be converted to mesitylene by passing it over an acid catalyst, e.g. an acid zeolite. Note, however, that the patent does not disclose or suggest that a Group VIII metal-containing ZSM-5 or another zeolite as hereinafter defined will selectively yield the dimeric ketone in superior amounts.